/* -*- Mode: C; c-basic-offset:8 ; indent-tabs-mode:t -*- */
/*
 * Linux usbfs backend for libusb
 * Copyright (C) 2007-2009 Daniel Drake <dsd@gentoo.org>
 * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
 * Copyright (c) 2013 Nathan Hjelm <hjelmn@mac.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "config.h"
#include "libusb.h"
#include "libusbi.h"
#include "linux_usbfs.h"

#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

#ifdef HAVE_ASM_TYPES_H
#include <asm/types.h>
#endif

#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif

#include <arpa/inet.h>

#ifdef HAVE_LINUX_NETLINK_H
#include <linux/netlink.h>
#endif

#ifdef HAVE_LINUX_FILTER_H
#include <linux/filter.h>
#endif

#define KERNEL 1

static int linux_netlink_socket = -1;
static int netlink_control_pipe[2] = { -1, -1 };
static pthread_t libusb_linux_event_thread;

static void *linux_netlink_event_thread_main(void *arg);

struct sockaddr_nl snl = { .nl_family=AF_NETLINK, .nl_groups=KERNEL };

static int set_fd_cloexec_nb (int fd)
{
    int flags;

#if defined(FD_CLOEXEC)
    flags = fcntl (linux_netlink_socket, F_GETFD);
    if (0 > flags) {
        return -1;
    }

    if (!(flags & FD_CLOEXEC)) {
        fcntl (linux_netlink_socket, F_SETFD, flags | FD_CLOEXEC);
    }
#endif

    flags = fcntl (linux_netlink_socket, F_GETFL);
    if (0 > flags) {
        return -1;
    }

    if (!(flags & O_NONBLOCK)) {
        fcntl (linux_netlink_socket, F_SETFL, flags | O_NONBLOCK);
    }

    return 0;
}

int linux_netlink_start_event_monitor(void)
{
    int socktype = SOCK_RAW;
    int ret;

    snl.nl_groups = KERNEL;

#if defined(SOCK_CLOEXEC)
    socktype |= SOCK_CLOEXEC;
#endif
#if defined(SOCK_NONBLOCK)
    socktype |= SOCK_NONBLOCK;
#endif

    linux_netlink_socket = socket(PF_NETLINK, socktype, NETLINK_KOBJECT_UEVENT);
    if (-1 == linux_netlink_socket && EINVAL == errno) {
        linux_netlink_socket = socket(PF_NETLINK, SOCK_RAW, NETLINK_KOBJECT_UEVENT);
    }

    if (-1 == linux_netlink_socket) {
        return LIBUSB_ERROR_OTHER;
    }

    ret = set_fd_cloexec_nb (linux_netlink_socket);
    if (0 != ret) {
        close (linux_netlink_socket);
        linux_netlink_socket = -1;
        return LIBUSB_ERROR_OTHER;
    }

    ret = bind(linux_netlink_socket, (struct sockaddr *) &snl, sizeof(snl));
    if (0 != ret) {
            close(linux_netlink_socket);
        return LIBUSB_ERROR_OTHER;
    }

    /* TODO -- add authentication */
    /* setsockopt(linux_netlink_socket, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one)); */

    ret = usbi_pipe(netlink_control_pipe);
    if (ret) {
        usbi_err(NULL, "could not create netlink control pipe");
            close(linux_netlink_socket);
        return LIBUSB_ERROR_OTHER;
    }

    ret = pthread_create(&libusb_linux_event_thread, NULL, linux_netlink_event_thread_main, NULL);
    if (0 != ret) {
            close(netlink_control_pipe[0]);
            close(netlink_control_pipe[1]);
            close(linux_netlink_socket);
        return LIBUSB_ERROR_OTHER;
    }

    return LIBUSB_SUCCESS;
}

int linux_netlink_stop_event_monitor(void)
{
    int r;
    char dummy = 1;

    if (-1 == linux_netlink_socket) {
        /* already closed. nothing to do */
        return LIBUSB_SUCCESS;
    }

    /* Write some dummy data to the control pipe and
     * wait for the thread to exit */
    r = usbi_write(netlink_control_pipe[1], &dummy, sizeof(dummy));
    if (r <= 0) {
        usbi_warn(NULL, "netlink control pipe signal failed");
    }
    pthread_join(libusb_linux_event_thread, NULL);

    close(linux_netlink_socket);
    linux_netlink_socket = -1;

    /* close and reset control pipe */
    close(netlink_control_pipe[0]);
    close(netlink_control_pipe[1]);
    netlink_control_pipe[0] = -1;
    netlink_control_pipe[1] = -1;

    return LIBUSB_SUCCESS;
}

static const char *netlink_message_parse (const char *buffer, size_t len, const char *key)
{
    size_t keylen = strlen(key);
    size_t offset;

    for (offset = 0 ; offset < len && '\0' != buffer[offset] ; offset += strlen(buffer + offset) + 1) {
        if (0 == strncmp(buffer + offset, key, keylen) &&
            '=' == buffer[offset + keylen]) {
            return buffer + offset + keylen + 1;
        }
    }

    return NULL;
}

/* parse parts of netlink message common to both libudev and the kernel */
static int linux_netlink_parse(char *buffer, size_t len, int *detached, const char **sys_name,
                   uint8_t *busnum, uint8_t *devaddr) {
    const char *tmp;
    int i;

    errno = 0;

    *sys_name = NULL;
    *detached = 0;
    *busnum   = 0;
    *devaddr  = 0;

    tmp = netlink_message_parse((const char *) buffer, len, "ACTION");
    if (tmp == NULL)
        return -1;
    if (0 == strcmp(tmp, "remove")) {
        *detached = 1;
    } else if (0 != strcmp(tmp, "add")) {
        usbi_dbg("unknown device action %s", tmp);
        return -1;
    }

    /* check that this is a usb message */
    tmp = netlink_message_parse(buffer, len, "SUBSYSTEM");
    if (NULL == tmp || 0 != strcmp(tmp, "usb")) {
        /* not usb. ignore */
        return -1;
    }

    tmp = netlink_message_parse(buffer, len, "BUSNUM");
    if (NULL == tmp) {
        /* no bus number (likely a usb interface). ignore*/
        return -1;
    }

    *busnum = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
    if (errno) {
        errno = 0;
        return -1;
    }

    tmp = netlink_message_parse(buffer, len, "DEVNUM");
    if (NULL == tmp) {
        return -1;
    }

    *devaddr = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
    if (errno) {
        errno = 0;
        return -1;
    }

    tmp = netlink_message_parse(buffer, len, "DEVPATH");
    if (NULL == tmp) {
        return -1;
    }

    for (i = strlen(tmp) - 1 ; i ; --i) {
        if ('/' ==tmp[i]) {
            *sys_name = tmp + i + 1;
            break;
        }
    }

    /* found a usb device */
    return 0;
}

static int linux_netlink_read_message(void)
{
    unsigned char buffer[1024];
    struct iovec iov = {.iov_base = buffer, .iov_len = sizeof(buffer)};
    struct msghdr meh = { .msg_iov=&iov, .msg_iovlen=1,
                 .msg_name=&snl, .msg_namelen=sizeof(snl) };
    const char *sys_name = NULL;
    uint8_t busnum, devaddr;
    int detached, r;
    size_t len;

    /* read netlink message */
    memset(buffer, 0, sizeof(buffer));
    len = recvmsg(linux_netlink_socket, &meh, 0);
    if (len < 32) {
        if (errno != EAGAIN)
            usbi_dbg("error recieving message from netlink");
        return -1;
    }

    /* TODO -- authenticate this message is from the kernel or udevd */

    r = linux_netlink_parse(buffer, len, &detached, &sys_name,
                &busnum, &devaddr);
    if (r)
        return r;

    usbi_dbg("netlink hotplug found device busnum: %hhu, devaddr: %hhu, sys_name: %s, removed: %s",
         busnum, devaddr, sys_name, detached ? "yes" : "no");

    /* signal device is available (or not) to all contexts */
    if (detached)
        linux_device_disconnected(busnum, devaddr, sys_name);
    else
        linux_hotplug_enumerate(busnum, devaddr, sys_name);

    return 0;
}

static void *linux_netlink_event_thread_main(void *arg)
{
    char dummy;
    int r;
    struct pollfd fds[] = {
        { .fd = netlink_control_pipe[0],
          .events = POLLIN },
        { .fd = linux_netlink_socket,
          .events = POLLIN },
    };

    /* silence compiler warning */
    (void) arg;

    while (poll(fds, 2, -1) >= 0) {
        if (fds[0].revents & POLLIN) {
            /* activity on control pipe, read the byte and exit */
            r = usbi_read(netlink_control_pipe[0], &dummy, sizeof(dummy));
            if (r <= 0) {
                usbi_warn(NULL, "netlink control pipe read failed");
            }
            break;
        }
        if (fds[1].revents & POLLIN) {
                usbi_mutex_static_lock(&linux_hotplug_lock);
                linux_netlink_read_message();
                usbi_mutex_static_unlock(&linux_hotplug_lock);
        }
    }

    return NULL;
}

void linux_netlink_hotplug_poll(void)
{
    int r;

    usbi_mutex_static_lock(&linux_hotplug_lock);
    do {
        r = linux_netlink_read_message();
    } while (r == 0);
    usbi_mutex_static_unlock(&linux_hotplug_lock);
}

